中文摘要：

为提高X射线脉冲星导航系统的导航精度，提出了一种基于低通滤波器的恒比定时方法，以提高X射线脉冲星导航系统中X射线脉冲到达时间的测量精度．通过设计测量方案，对原有的峰值定时方法和改进后的恒比定时系统的定时精度和死时间进行测量．测量结果表明，峰值定时系统的定时精度和死时间分别为18和4750DS，恒比定时系统的定时精度和死时间分别为0．78和105ns，与原有的峰值定时系统相比，采用恒比定时系统的定时精度和死时间均得到明显的提高．在X射线脉冲星导航系统中，通过利用这两种不同定时系统来测量X射线光子的到达时间以构造累积脉冲轮廓．实验结果表明，与峰值定时系统相比，采用改进的恒比定时系统获得的累积脉冲轮廓的信噪比得到明显改善，因此，采用恒比定时系统的导航精度可得到提高．

英文摘要：

In order to improve the navigation accuracy of the X-ray pulsar navigation system, in this paper we propose a constant fraction timing method based on the low-pass filter to measure the arrival time of the X-ray pulse in X-ray pulsar navigation. According to the technical scheme, the timing accuracies and dead times of original peaking timing and the improved constant fraction timing are measured. Experimental results indicate that the timing accuracy and the dead time of the peaking timing system are 18 ns and 4750 ns, the timing accuracy and the dead time of the constant fraction timing system are 0.78 ns and 105 ns. The timing accuracy and the dead time of constant fraction timing system are significantly improved compared with those of the peaking timing system. In the X-ray pulsar navigation system, the cumulative pulse profile of the X-ray pulse is constructed in the two different timing systems through measuring the arrival time of the X-ray photon. Experimental results indicate that compared with using the peaking timing system, the cumulative pulse profile of the X-ray pulse using the improved constant fraction timing system is improved obviously, therefore, the navigation accuracy could be improved by using the constant fraction timing system.